CLEAR Model for Predicting Ventilatory Liberation in Severe COPD

This prospective observational cohort study aims to prospectively evaluate and validate the Clinical Load, Exchange, Ability of Respiration, and Reserve (CLEAR) model for predicting sustained ventilatory liberation in patients with severe chronic obstructive pulmonary disease (COPD) receiving invasive mechanical ventilation (MV) or non-invasive ventilation (NIV). Two parallel cohorts will be studied: CLEAR-MV for patients undergoing spontaneous breathing trials (SBT) and CLEAR-NIV for patients undergoing NIV withdrawal trials. The model integrates diaphragm ultrasound evaluating diaphragm thickening fraction (DTF), ventilatory load indices including the rapid shallow breathing index (RSBI) or Clinical Load Index (CLI), gas exchange parameters including Potential of Hydrogen (pH), partial pressure of carbon dioxide (PaCO₂), and its change over time (ΔPaCO₂) combined as the Gas Exchange Index (GEI), and peripheral muscle reserve assessing rectus femoris (RF) and vastus intermedius (VI) thickness. The primary outcome is successful liberation from ventilatory support within 72 hours. Secondary outcomes include ventilatory failure within 7 days, ventilator- or NIV-free days at 28 days, and time-fixed 90-day clinical outcomes including all-cause mortality, sustained ventilatory independence, and rehospitalization for respiratory failure. Model performance will be evaluated using discrimination (area under the receiver operating characteristic curve), calibration (calibration intercept and slope), and clinical utility (decision curve analysis and net benefit) and compared with prespecified established ventilatory indices, including the Rapid Shallow Breathing Index (RSBI) and Integrative Weaning Index (IWI) in the invasive mechanical ventilation cohort, and the Heart rate, Acidosis, Consciousness, Oxygenation, and Respiratory rate (HACOR) score and the ratio of peripheral oxygen saturation to fraction of inspired oxygen divided by respiratory rate (ROX) index in the non-invasive ventilation cohort.